In mobile equipment traveling along a track of a stacker crane, an overhead traveling crane and the like used for conveying goods and the like, signals such as control instructions are transferred between a system control device and a control device on the mobile equipment side through an optical data transmission device for the purpose of wire-saving and the like.
Patent Document 1 discloses an automatic conveyance device in which a system control device which is fixed equipment and a crane control device mounted to a stacker crane which is mobile equipment are connected to each other through wired lines between which an optical data transmission device is interposed.
In the automatic conveyance device, control instructions which are output from the system control device to the wired line are transmitted to the wired line connected to the crane control device side through the optical data transmission device.
Such an automatic conveyance device is provided with a normal stop function for interrupting automatic control using the system control device for the purpose of maintenance and the like to temporarily stop moving devices, or an emergency stop function for previously preventing the occurrence of a serious and dangerous situation such as a collision with mobile equipment caused by intrusion of persons or obstacles into a traveling path, device failures or the like. Particularly, the emergency stop function requires an extremely high level of safety so as to reliably operate when needed.
For example, safety systems are widely known in which when a sensor such as a photoelectric SW that detects intruders or obstacles is installed on mobile equipment and the intruders or obstacles within the traveling path are detected by the sensor, the mobile equipment is caused to be immediately stopped.
Patent Document 1 discloses a control method for avoiding an accidental contact of two stacker cranes moving on the same track, in which two stacker cranes which are supported by wheels disposed in the forward-rearward direction of movement and move on the same track are provided with position detection means for detecting a position on the track and an optical transmitter for transmitting position information detected by the position detection means to the other stacker crane and receiving the position information transmitted from the other stacker crane, and each of the stacker cranes is brought to an emergency stop when the proximity to the other stacker crane is recognized based on the other position information received by the optical transmitter and its own position information. Meanwhile, as the position detection means, a rotary encoder that detects the rotation of the wheels, a distance measuring device that detects the distance from a reference position, or the like is used.
Patent Document 2 discloses an emergency stop device capable of bringing a mobile crane to an emergency stop in accordance with the intention of an operator. The emergency stop device is configured such that an emergency stop switch, for stopping an engine or the like in an emergency, is connected in series through a connector between control means such as an engine of a mobile crane or a solenoid and a power source. The emergency stop switch is connected to a connector through a certain length of wiring so as to be portably carried inside and outside a machine body spaced apart from the machine body.